What is an IVF Frozen Transfer?
In the process of a Freeze All cycle, the best embryos are cultured to day 5 or 6, frozen by a propriety protocol perfected by our laboratory director, Dr. Dmitri Dozortsev,
and then transferred into the uterus in another cycle.
This method allows us to properly investigate the uterine cavity with hysteroscopy (hyperlink) and prepare the uterine lining until the optimal conditions are met for embryo transfer.
AFCT has been using Freeze All cycles since 2014 and we have found many advantages over the years due to the more natural hormonal environment created for the embryos. Among the advantages are higher pregnancy rates, eliminating the risk of ovarian hyperstimulation, lowering the risk of ectopic (tubal) pregnancy, and the infants born have higher weights.
During the Freeze All cycle, the blastocysts formed on day 5 or 6 can also have a biopsy of the outer coat of the embryo, called trophectoderm, by removing 3-5 cells. This method allows us to select the single best genetically normal embryo for transfer while minimizing the chance of a pregnancy loss. Dr. Dmitri Dozortsev is one of the leading experts in embryo biopsy and has developed a unique method of performing the biopsy to ensure minimal impact on embryo viability.
The embryos can be frozen for several years without the risk of damage until the family is completed.
With the Freeze All process, our IVF laboratory has achieved a very high pregnancy rate in all age groups.
How Does a Frozen Embryo Transfer Work?
The process of freezing and thawing the embryos is called vitrification, and it has been perfected to the point where almost all the embryos that we freeze can now survive the thawing process.
The process of frozen embryo transfer involves only the preparation of the uterus so that it can be aligned with the frozen embryos. This can be easily accomplished by administering estrogen pills for about 2 weeks. The embryos will be thawed and transferred according to a set calendar provided for our patients.
Culturing the embryos to the blastocyst stage, or day 5 or 6 after egg retrieval, may be recommended for patients that have at least 8 fertilized oocytes on the first day after retrieval. The decision to culture embryos to day 5 is based on the development of the embryos and the patient’s individual history. Blastocysts have higher implantation and pregnancy rates, and fewer embryos are usually transferred back to the patient than would be transferred on day 3. Culturing embryos to day 5 may not always be beneficial, as some patients may have embryos that do not tolerate in vitro culture well.
How Does Frozen Embryo Transfer Help Prevent Ovarian Hyperstimulation?
When we stimulate the growth of the oocytes (eggs), we are increasing the estrogen levels to 10-20 times higher than normal in a natural cycle. Such high estrogen levels appear to have a negative impact on the uterus, which now may not be aligned with the growth of the eggs. High estrogen levels inhibit the effects of progesterone, which is the most essential hormone in the process of implantation and pregnancy.
The risk of ovarian hyperstimulation syndrome increases with high estrogen levels, and this is also true in patients with PCOS. In this syndrome, patients can experience severe abdominal discomfort, fluid collection in the abdomen, and shortness of breath, which may require hospitalization. When we perform frozen embryo transfer, we can slightly alter the stimulation protocol and almost completely eliminate this syndrome.
What are the Benefits of IVF Embryo Frozen Transfer?
- There are now several studies that confirm the theory that we can obtain significantly higher pregnancy rates when we wait and transfer the embryos in a frozen cycle (about 6 weeks from egg retrieval) as compared to transferring the embryos in a fresh cycle. This is particularly important in patients who we anticipate will have a good response to ovarian stimulation (estrogen levels greater than 5000 pg/mL).
- Patients who have polycystic ovarian syndrome (PCOS) naturally have a higher number of eggs compared to other patients prior to egg stimulation. The higher number of eggs leads to high levels of estrogen in the end of IVF stimulation. Therefore, patients with PCOS greatly benefit from frozen embryo transfer.
- Some data suggests that the pregnancies resulting from frozen embryo transfer are healthier and the infants are about 150 grams bigger.
What are the success rates for a Frozen Embryo Transfer?
Frozen embryo transfer leads to higher pregnancy rates.
The success rates of a Frozen Transfer cycle are higher than those of fresh IVF cycle and have the same primary indicator for success: the maternal age at the time of embryo freezing. Many patients wait several years between the initial freeze of their embryos and attempting a subsequent Frozen Transfer cycle. Any patient, regardless of the amount of time between embryo freezing and thawing, can expect nearly the same potential for success as they experienced with a fresh IVF cycle, which the frozen embryos initially came from. Patients can expect the same chances of success because frozen embryos are suspended in time and do not age.
Women 37 years and younger can expect about 65% delivery rate per thaw. This rate declines with increasing maternal age at the time of embryo freezing.